The present invention relates to an apparatus and method for subjecting a work-piece substrate to a semiconductor process. The term "semiconductor process" used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a work-piece substrate, such as a semiconductor wafer or an LCD substrate, by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the substrate.
Among the processes of manufacturing semiconductor devices which have been highly integrated in recent years, processes using a vacuum-processing apparatus (semiconductor processing apparatus) are currently in the main. For example, in a process of forming a gate wiring layer, a poly-crystalline silicon film is formed as a material of the gate wiring layer by a CVD (Chemical Vapor Deposition) method. Then, a predetermined mask pattern made of a photoresist layer is formed on the silicon film by a lithography method. Then, unnecessary parts of the poly-crystalline silicon film for forming the wiring layer are removed by an anisotropic etching method, such as an RIE (Reactive Ion Etching) method, so that the wiring layer is completed. After the wiring layer is formed, the photoresist layer, which has become unnecessary is removed. In this process, when the poly-crystalline silicon film is formed, when the poly-crystalline silicon film is patterned, and when the photoresist layer is removed after the wiring layer is formed, a CVD apparatus, a dry-etching apparatus, and a dry-ashing apparatus are used, respectively.
Further, in a process of forming an aluminum (Al) wiring layer, which is currently used in general, several vacuum-processing apparatuses are used. Specifically, when an aluminum film is formed, a sputtering apparatus is used. When the aluminum film is patterned with a predetermined mask pattern, a dry-etching apparatus is used. When a used photoresist is removed after the wiring layer is formed, a dry-ashing apparatus is used.
As described above, in order to form the wiring structure of a semiconductor device, at least several tens of processes using vacuum-processing apparatuses are necessary. Besides, a dry-etching technique using plasma is indispensable especially in micro-lithography.
Further, in order to form other device structures in the semiconductor device, several kinds of vacuum-processing apparatuses, such as a film formation apparatus and an RIE apparatus, are also necessary. For example, an RIE apparatus for an oxide film basically has a structure shown in FIG. 5. The vacuum-processing apparatus shown in FIG. 5 includes two vacuum-process chambers. The vacuum-processing apparatus is constituted of load and unload chambers (which may be referred to as cassette chambers), a common transfer chamber (which may be referred to as a transfer robot chamber), and the vacuum-process chambers (which may be referred to as process chambers). When a semiconductor wafer is transferred into a process chamber, the cassette chambers 61 and 62 are set at a pressure-reduced state in advance, so that the wafer is transferred while the pressure of the process chamber is kept at a pressure-reduced state. The common transfer chamber 63 is used for distributing wafers from the cassette chambers 61 and 62 to the process chambers. The process chambers 64 and 65 are used each for subjecting a wafer to a predetermined semiconductor process.
In recent years, it is usual to arrange a plurality of process chambers as shown in FIG. 5, so that the productivity is improved. In other words, FIG. 5 is a standardized block diagram showing a dry-etching apparatus currently used. In this vacuum-processing apparatus, the cassette chambers 61 and 62 are connected to a common dry pump 68, so that they can function as vacuum chambers. Similarly, the common transfer chamber 63 is connected to a dry pump 70. The process chambers 64 and 65 are connected to turbo molecular pumps 66 and 67, respectively, and to a common dry pump 71 through the turbo molecular pumps 66 and 67.
Generally, the cassette chambers and the common transfer chamber do not require any high vacuum, and thus only the dry pumps are used for exhausting these chambers. On the other hand, the process chambers require a high vacuum, and thus the turbo molecular pumps and the dry pump are used for them. Namely, the three dry pumps and the two turbo molecular pumps are used for the vacuum chambers of the semiconductor processing apparatus shown in FIG. 5. These pumps are continuously driven from the time when a wafer cassette is loaded, through a period of time for processing all the wafers, to the time when the wafer cassette is unloaded.
Dry-pumps require a lot of electric power for their operation. In recent semiconductor mass-production factories, manufacturing processes using vacuum-processing apparatuses as described above are performed as the main processes, and thus the number of apparatuses is large. Each of the vacuum processing apparatuses has a plurality of vacuum-exhaust mechanisms, so the total number of the vacuum-exhaust mechanisms in the factory is very large, and their running costs are enormous. To reiterate, in semiconductor processing installations, especially in mass-production installations, the running cost of dry pumps is enormous, and thus brings about a rise in the manufacturing cost.
Furthermore, in recent years, the greenhouse effect on the earth has become a serious international problem. In order to solve this problem, it is important to prevent, as far as possible, carbon oxide gases which are the main cause of the greenhouse effect from being produced. One of the main causes for production of carbon oxide gases is due to mass consumption of electric power. Therefore, it is necessary for the industrial field to suppress electric power consumption as far as possible. This is the same for semiconductor processes. In this respect, the above described increase in the manufacturing cost can be reduced, thereby contributing to solving the environmental problem.